ubuntu-cve-2026-27962
Vulnerability from osv_ubuntu
Published
2026-03-16 18:16
Modified
2026-07-16 22:59
Summary
Details

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a JWK Header Injection vulnerability in authlib's JWS implementation allows an unauthenticated attacker to forge arbitrary JWT tokens that pass signature verification. When key=None is passed to any JWS deserialization function, the library extracts and uses the cryptographic key embedded in the attacker-controlled JWT jwk header field. An attacker can sign a token with their own private key, embed the matching public key in the header, and have the server accept the forged token as cryptographically valid — bypassing authentication and authorization entirely. This issue has been patched in version 1.6.9.

Severity
9.1 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
9.1 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
N/A (UNKNOWN)
medium
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro: https://ubuntu.com/pro",
        "binaries": [
          {
            "binary_name": "python3-authlib",
            "binary_version": "0.15.5-1ubuntu0.1~esm2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:22.04:LTS",
        "name": "python-authlib",
        "purl": "pkg:deb/ubuntu/python-authlib@0.15.5-1ubuntu0.1~esm2?arch=source\u0026distro=esm-apps/jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.15.5-1ubuntu0.1~esm2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.15.4-1",
        "0.15.5-1",
        "0.15.5-1ubuntu0.1~esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro: https://ubuntu.com/pro",
        "binaries": [
          {
            "binary_name": "python3-authlib",
            "binary_version": "1.3.0-1ubuntu0.1~esm2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:24.04:LTS",
        "name": "python-authlib",
        "purl": "pkg:deb/ubuntu/python-authlib@1.3.0-1ubuntu0.1~esm2?arch=source\u0026distro=esm-apps/noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.3.0-1ubuntu0.1~esm2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.2.1-1",
        "1.3.0-1",
        "1.3.0-1ubuntu0.1~esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "python3-authlib",
            "binary_version": "1.6.0-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:25.10",
        "name": "python-authlib",
        "purl": "pkg:deb/ubuntu/python-authlib@1.6.0-1?arch=source\u0026distro=questing"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.5.1-1",
        "1.5.2-1",
        "1.6.0-1"
      ]
    },
    {
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro: https://ubuntu.com/pro",
        "binaries": [
          {
            "binary_name": "python3-authlib",
            "binary_version": "1.6.7-1ubuntu0.1~esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:26.04:LTS",
        "name": "python-authlib",
        "purl": "pkg:deb/ubuntu/python-authlib@1.6.7-1ubuntu0.1~esm1?arch=source\u0026distro=esm-apps/resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.6.7-1ubuntu0.1~esm1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.6.0-1",
        "1.6.5-1",
        "1.6.6-1",
        "1.6.7-1"
      ]
    }
  ],
  "aliases": [],
  "details": "Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a JWK Header Injection vulnerability in authlib\u0027s JWS implementation allows an unauthenticated attacker to forge arbitrary JWT tokens that pass signature verification. When key=None is passed to any JWS deserialization function, the library extracts and uses the cryptographic key embedded in the attacker-controlled JWT jwk header field. An attacker can sign a token with their own private key, embed the matching public key in the header, and have the server accept the forged token as cryptographically valid \u2014 bypassing authentication and authorization entirely. This issue has been patched in version 1.6.9.",
  "id": "UBUNTU-CVE-2026-27962",
  "modified": "2026-07-16T22:59:29Z",
  "published": "2026-03-16T18:16:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-27962"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-27962"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/authlib/authlib/security/advisories/GHSA-wvwj-cvrp-7pv5"
    },
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-8557-1"
    }
  ],
  "related": [
    "USN-8557-1"
  ],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-27962"
  ]
}



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Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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